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Thread: Veneer glue problem

  1. #1
    Join Date
    Jan 2018
    Location
    Cleveland, Ohio
    Posts
    61

    Veneer glue problem

    This week at a class on veneering projects the instructor said Unibond 800 (a catalytic glue from Vacuum Pressing Systems) was reformulated a couple years ago. He said he never uses it any more, because of a problem with dark blotches. He showed me a panel with dozens of dark blotches. They appeared more than 6 months after it was completed. (Everybodyís worst nightmare)

    Heís no amateur. The panel was gorgeous until the blotches appeared. He sent it to a chemist at Franklin (makers of a competitor, Titebond) who confirmed the problem is the glue. But itís not the bleed-through that everybody gets (rapidly) with open grain veneers.

    Is this problem widely seen? Is X-press glue also a problem? I really donít want to switch to a glue that water or heat will affect.

  2. #2
    Unibond 800 was reformulated about 10 years ago. There have been some problems reported with chemical staining (blotches) of light colored veneer due to incomplete mixing of the acid catalyst crystals during catalyzation. The cure seems to be to mix the resin and catalyst with a drill paddle, let the mix sit for a few minutes and mix thoroughly again. Using the blocker to prevent bleedthrough may help as well, I have never had this problem but it does make me a bit leary of this product. I have not seen reports of similar problems with powdered plastic resin glue. I usually use a rigid pva except when I need the working time, moisture resistance and extra rigidity of urea formaldehyde or epoxy.

  3. #3
    Join Date
    Dec 2010
    Location
    WNY
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    8,262
    I haven't had that problem with Unibond 800. I don't use a power mixer, but I mix thoroughly, let it sit for 5 - 10 minutes, then remix again. Oh yeah, I only use shop sawn veneer so maybe that greatly reduces any chance of that type of problem. I never get bleed through except though holes, cracks, etc.

    Forget Weldwood Plastic Resin Glue; it's no longer available.

    John

  4. #4
    The formaldehyde assured glue consistency and thorough even mix. So my guess is that the new stuff needs some formaldehyde.
    These days I read the Twinkie label to make sure they havenít replaced the sugar with some something ďmore nutritious ď.

  5. #5
    Quote Originally Posted by Mel Fulks View Post
    The formaldehyde assured glue consistency and thorough even mix. So my guess is that the new stuff needs some formaldehyde.
    These days I read the Twinkie label to make sure they haven’t replaced the sugar with some something “more nutritious “.
    Unibond 800 is a urea formaldhyde adhesive.

    Powdered plastic resin (ppr, uf) glue is available from various suppliers like Veneer Systems and Veneer Supplies.

  6. #6
    Kevin , thanks. Iím retired now, remember when it was unavailable for a while. The supplier we used then said US gov. wanted it gone.
    Iím astounded by the current cost, but might have to use it for something.

    Mel

  7. #7
    Join Date
    Mar 2003
    Location
    San Francisco, CA
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    9,944
    I gave up urea-formaldehyde glue at least ten years ago because of the formaldehyde exposure. I've used epoxy ever since -- West Systems 105. It works well.

  8. #8
    Join Date
    Dec 2010
    Location
    WNY
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    Quote Originally Posted by Jamie Buxton View Post
    I gave up urea-formaldehyde glue at least ten years ago because of the formaldehyde exposure. I've used epoxy ever since -- West Systems 105. It works well.

    Not without its own risks: https://www.westsystem.com/safety/he...sure-to-epoxy/

    John

  9. #9
    Join Date
    Apr 2017
    Location
    Clarks Summit PA
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    1,375
    The only time I used Unibond 800 I used commercial cherry veneer ( 1/32" ). I think I applied too much. I did have terrible bleed through and had to apply another layer of veneer over that using hot hide glue. What a pain.

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